An electronic apparatus, such as an ATX (Advanced Technology eXtended) power supply, a display screen or a television set, has a power socket provided thereon. The power socket usually includes three first terminals, which are located at a front side of the power socket for a female connector on a power cord to plug in, and three second terminals, which are located at a rear side of the power socket. A first and a second one of the first terminals are a positive power terminal and a negative power terminal, respectively, and electrically connected to a first and a second one of the second terminals; and a third one of the first terminals is a ground terminal and electrically connected to a third one of the second terminals. In the case of an ATX power supply, the three second terminals of the power socket are inserted into and soldered to a circuit board of the ATX power supply, so that each of the second terminals has a solder ball formed thereon. Via the solder balls, the first and the second one of the second terminal are separately electrically connected to two power layers on the circuit board and the third one of the second terminals is electrically connected to a grounding layer of the circuit board.
To meet the IEC 62368-1 standard, the currently available ATX power supply usually adopts one of two ways to ensure its safe grounding. The first way is to use a green yellow grounding wire that meets AWG standards. The green yellow grounding wire has an end soldered to the third one of the second terminals of the power socket of the ATX power supply and another end screw-locked to a metal chassis of an electronic apparatus. In the event a failure or a short circuit occurs in the ATX power supply, an instantaneous big current or short-circuit current resulting from the short circuit will be guided by the third one of the second terminals (i.e. the ground terminal) from the grounding layer of the circuit board to the green yellow grounding wire, from where the instantaneous big current is discharged to the metal chassis to achieve the effect of electric shock prevention and safe use of the ATX power supply. The second way is to use a circuit board that has large unused areas clad with copper (i.e. a copper grounding foil), so that the ground terminal is electrically connected to the copper grounding foil to withstand an increased instantaneous big current. In this case, the copper-clad circuit board must be subjected to a 1500 A grounding test to meet the required IEC standards.
While the above two ways all provide the required grounding effect, they have some disadvantages. The green yellow grounding wire has a fixed length that is not always suitable for using with all kinds of electronic apparatuses. Besides, electronic apparatuses from different manufacturers are not always the same in terms of the position at where the grounding wire is connected to a contact on the circuit board, which might result in an uneasily found disconnection or separation of the grounding wire in the electronic apparatuses and accordingly, cause an electric shock and an increased cost. On the other hand, the copper-clad circuit board is subjected to the risk of a fully melted grounding solder ball on the circuit board when the instantaneous big current flows through the copper grounding foil, which tends to cause a failed grounding due to the one-time occurrence of an instantaneous big current. Therefore, the copper-clad circuit board is not safe for use and the large-area copper grounding foil thereof disadvantageously prevents it from being manufactured at a reduced cost.